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Sea Otter Savvy

Sea Otter Science And Community Outreach

Monterey is Expensive: Investigating the Cost of Disturbance

hbarrett otter tracking 400x300Moss Landing Marine Laboratories' graduate student Heather Barrett spotting sea otters 

Guest writer and graduate student, Heather Barrett, introduces a new collaboration between Moss Landing Marine Laboratories, UC Santa Cruz, and Sea Otter Savvy studying the effect of human-caused disturbance on sea otters living in and around Monterey Bay. 

The crisp morning begins with stretches, a barrel role here and there, and one of the members breaking off to search for a crab breakfast. The raft bobs as the distant boat wake lifts each otter in a wave; rocking them gently in a water cradle. There are five mothers with cotton-ball pups that begin the tedious nursing and grooming process, lifting the plush bodies and breathing warm air in to their Einstein frizz. But the calm morning routines will soon be disrupted and turn to disorder. The bright colored beasts have arrived, aiming the kayak bows towards the otter raft, paddles drumming as they hit the surface of the water.

jetty raft 2 kayaks 300x221Kayakers approach a sea otter raft in Moss Landing, CAMost human disturbance is unintentional. However, this naiveté does not eliminate the potential behavioral or physiological consequences for wildlife. Simply our presence, especially when too close, can impact certain species by initiating a stress response. Stress hormones release, causing an increase in heart rate, rise in blood pressure, suppression of feeding and reproduction, and modulation of immune function 1. This is critical in acute stress response, for it allows for a quick reaction during a potentially threatening situation. But what if this becomes chronic?

Chronic stress leads to prolonged exposure to these stress hormones, which can cause muscle wasting, bone thinning, reproductive failure, and immune deficiency 1. These physiological responses are usually undetected in wildlife, which can portray a false sense of acceptability for disturbance 2. Behavioral responses tend to be clearer since they are visually detectable. Individuals will become alert, move away, and show avoidance or even aggression 3. All which have an energetic cost. With these varying responses, why is disturbance particularly a concern for sea otters?

As a keystone species, sea otters have a disproportionate effect on their surrounding environment, enhancing local biodiversity 4. They exhibit this strong influence on their coastal community through their voracious appetite, controlling grazer populations 4. With little fat storage and only dense fur to keep warm, sea otters use their high metabolic rate to maintain their internal temperature in a cold marine environment. Since they use energy to keep warm, they must consume a quarter of their body weight in food each day to fuel this heat production 5.

So picture an exhausted sea otter mother: using energy for lactation, heat production, foraging, and pup care; imagine what it would be like to have constant disturbance from people recreating in the bay. If already living near physiological limits, what is the energetic consequence when human disturbance increases the cost? To answer this, it is important to understand the types of disturbance and create a baseline of behavioral response.

hbarrett jetty rdHeather monitoring the bachelor raft in Moss LandingSea Otter Savvy is spearheading the sea otter disturbance data collection with citizen science and educating the public through outreach programs. As a graduate student at Moss Landing Marine laboratories, I am thrilled to participant in the data collection and honored to use this information. I will couple this with the previously collected metabolic data from University of California Santa Cruz5,6 to investigate the energetic cost of disturbance of sea otters in Monterey Bay. This unique collaboration, and inclusion of graduate research, benefits the scientific community, the public, and can provide information to agencies making wildlife policy and management decisions.

If you are interested in learning more about Moss Landing Marine Laboratories, please visit the website: https://www.mlml.calstate.edu.
You are also encouraged to visit the Laboratories’ Open House this weekend April 29th and 30th. Come experience marine science and hear about the graduate student projects! 

1. Hill, R.W., Wyse, G.A., Anderson, M. and Anderson, M., 2004. Animal physiology (Vol.2). Massachusetts: Sinauer Associates.
2. Sorice, M.G., Shafer, C.S. and Scott, D., 2003. Managing endangered species within the use/preservation paradox: understanding and defining harassment of the West Indian manatee (Trichechus manatus). Coastal Management, 31(4), pp.319-338
3. Gill, J.A., Sutherland, W.J. and Watkinson, A.R., 1996. A method to quantify the effects of human disturbance on animal populations. Journal of appliedEcology,pp.786-792.
4. Estes, J.A. and Palmisano, J.F., 1974. Sea otters: their role in structuring nearshore communities. Science, 185(4156), pp.1058-1060.
5. Thometz, N.M., Tinker, M.T., Staedler, M.M., Mayer, K.A. and Williams, T.M., 2014. Energetic demands of immature sea otters from birth to weaning: implications for maternal costs, reproductive behavior and population-level.
6. Yeates, L.C., Williams, T.M. and Fink, T.L., 2007. Diving and foraging energetics of the smallest marine mammal, the sea otter (Enhydra lutris). Journal of Experimental Biology, 210(11), pp.1960-1970.